I've only played one game so far but it seemed at least to us that while buildings, military and wonders get better with every age, golden cards just get worse and worse.

In first age, you get 2 resources or option to lose one resource in victory points. Here also, buildings and military cost only 1 resource, so you'd get enough to build 2 things.

As ages progress, you still only get 2 resources, but the price of the buildings and military increases to 2, 3 and 4. So whilst you started of with one gold card netting you two builds, you move to 1, then to 2/3rds and to 1/2 of a build.

The victory point conversion also is getting worse and worse.

So are we just not understanding how these are suppose to work because it just didn't see worth buying at all after age 1 finished.

They cost more, but they are not worse. In a lot of ways, four resources in age IV costs less than one resource in age I. At the end of the game, you likely have something extra sitting around and you'd be a fool not to trade 0.5 VP worth of resources for 1 VP. In age I, every resource is vital.

I think others have summed it up pretty well, but I will agree with you they are less attractive. Age I 2 ore for those like Egypt without a military unit they are quite powerful (allows Egypt to often build/finish a wonder). And I admit I look at them less and less as the ages advance (unless you have something like a +3 golden age bonus).

That said as they point out...in a close game, where your machine is producing a lot of resources...every 1/2 VP point can be important and you will be fighting over them because they are guaranteed VP's unlike wonders in the last Age.

I hardly ever see them taken in Age 1, but they are always hoovered up from the 1 slot in Age 3 & 4...

If Greece is in the game, the Age 1 Golden Ages are the best as you are paying as little as 1 gold to get a point or the equivalent of a battle in rocks/books. I think Golden Ages are the most underrated card myself. I like picking them up; especially since many opponents ignore them.